Old English calu "bare, bald," from Proto-Germanic *kalwa- (source also of Middle Dutch calu, Dutch kaal, Old High German kalo, German Kahl), from PIE root *gal- (1) "bald, naked" (source also of Russian golyi "smooth, bald"). From young birds with no feathers, meaning extended to any young inexperienced thing or creature (1570s). Apparently not related to Latin calvus "bald."